Hip joint device

ABSTRACT

A medical device for implantation in a hip joint of a patient is provided. The medical device is adapted to be fixated to the pelvic bone of the patient. The medical device comprises an inner and an outer surface, wherein a contacting portion, of said inner surface is spherical and adapted to face the center of the hip joint when said medical device is implanted. The medical device is adapted to receive a caput femur or a prosthetic replacement therefor having a spherical portion, wherein said medical device comprises at least one extending portion, extending said contacting portion of said inner surface such that said at least one extending portion clasps said spherical portion of said caput femur, or a prosthetic replacement therefor, such that said spherical portion is restrained in said medical device. Restraining the caput femur in the medical device reduces the risk that the hip joint dislocates when in use by the patient.

TECHNICAL FIELD

The present invention relates generally to medical devices forimplantation a hip joint.

BACKGROUND ART

The hip joint is a synovial joint, joining the pelvis to the proximalportion of the femoral bone. Synovial joint are the most common types ofjoint in mammals, and are typical of nearly all limb joints. Thecontacting surfaces of said the pelvic, the acetabulum, and thecontacting surface of the femoral bone, the caput femur, are smooth androunded, and covered by articular cartilage. A synovial membrane,encapsulates the joint, forming a hip joint cavity, which containssynovial fluid. Outside the synovial membrane is a fibrous capsule andligaments, forming an articular capsule.

There are both natural and pathological processes leading todeteriorated joint function. With age and wear, the articular cartilagebecomes less effective as a shock absorber and a lubricated surface.Different degenerative joint diseases, such as arthritis,osteoartrithis, or osteoarthrosis, accelerate the deterioration.

Hip joint Osteoarthritis is a syndrome in which low-grade inflammationresults in pain in the hip joints, caused by abnormal wearing of theCartilage that acts as a cushion inside if the hip joint. This abnormalwearing of the cartilage also results in a decrease of the jointslubricating fluid called Synovial fluid. Hip joint Osteoarthritis isestimated to affect 80% of all people over 65 years of age, in more orless serious forms.

The present treatment for hip osteoarthritis comprises NSAID drugs,local injections of Hyaluronic acid or Glucocorticoid to helplubricating the hip joint, and replacing part of the hip joint with aprosthesis through hip joint surgery.

The replacing of parts of the hip joint is one of the most commonsurgeries to date performed at hundreds of thousands of patients in theworld every year. The most common method comprises placing a metalprosthesis in Femur and a plastic bowl in Acetabulum. This operation isdone through an incision in the hip and upper thigh and through FasciaTata and the lateral muscles of the thigh. To get access to the joint,the supporting Capsule attached to Femur and Ilium needs to bepenetrated, making it difficult to get a fully functional joint afterthe surgery. Femur is then cut at the neck with a bone saw and theprosthesis is placed in femur either with bone cement or without.Acetabulum is slightly enlarged using an Acetabular reamer, and theplastic bowl is positioned using screws or bone cement.

The complications after hip joint surgery includes dislocation of thehip joint and loosening of the prosthesis from its fixation in thefemoral bone. The loosening and/or dislocation of the prosthesis couldbe induced by an abnormal strain being placed on the hip joint from e.g.the patient falling or making a rapid movement of the hip, or by abodily macrophage reaction.

SUMMARY

A medical device for implantation in a hip joint of a patient isprovided. The medical device is adapted to be fixated to the pelvic boneof the patient. The medical device comprises an inner and an outersurface, wherein a contacting portion, of said inner surface isspherical and adapted to face the center of the hip joint when saidmedical device is implanted. The medical device is adapted to receive acaput femur or a prosthetic replacement therefor having a sphericalportion, wherein said medical device comprises at least one extendingportion, extending said contacting portion of said inner surface suchthat said at least one extending portion clasps said spherical portionof said caput femur, or a prosthetic replacement therefor, such thatsaid spherical portion is restrained in said medical device. Restrainingthe caput femur in the medical device reduces the risk that the hipjoint dislocates when in use by the patient.

According to one embodiment, the medical device is adapted to receive acaput femur or a prosthetic replacement therefor having a collum femuror prosthetic collum femur fixated to said spherical portion of saidcaput femur or prosthetic replacement therefor. The inner surfacecomprises an equator line, being the largest circular circumference ofsaid inner contacting surface, being a surface adapted to be in contactwith said caput femur, or prosthetic replacement therefor. The at leastone extending portion passes beyond said equator line, such that the endportion of said contacting portion of said inner surface forms acircular extension line having a smaller circumference than said equatorline, and at least one extending portion circumferentially extendsdiscontinuously along said equator line, such that a portion of saidcollum femur or prosthetic replacement therefor can be placed betweensaid extension line and said equator line.

According to another embodiment, the medical device is adapted toreceive a caput femur or a prosthetic replacement therefor having acollum femur or prosthetic collum femur fixated to said sphericalportion of said caput femur or prosthetic replacement therefor. Theinner surface comprises an equator line, being the largest circularcircumference of said inner surface and at least one extending portionpassing beyond said equator line, such that the end portion of saidcontacting portion of said inner surface forms a circular extension linehaving a smaller circumference than said equator line. The at least oneextending portion circumferentially extends discontinuously along saidequator line, such that a portion of said collum femur or prostheticreplacement therefor can be placed between said extension line and saidequator line.

According to one embodiment, the extension line is placed distal to theequator line, when the medical device is implanted.

According to one embodiment, the at least one extending portion extendscircumferentially along said equator line, dorsal to the right-left axisof pelvis.

According to one embodiment, the at least one extending portion extendscircumferentially along said equator line, dorsal to the coronal pelvisplane PXY and proximal to the horizontal pelvis PXZ plane.

According to one embodiment, the at least one extending portion extendscircumferentially along the equator line, dorsal to the coronal pelvisplane PXY and distal to the horizontal pelvis PXZ plane.

According to another embodiment, the medical device extendscircumferentially along said equator line dorsal to the coronal pelvisplane PXY and proximal to the horizontal pelvis PXZ plane, such that oneextending portion extends dorsal to the coronal pelvis plane PXY anddistal to the horizontal pelvis PXZ plane.

According to yet another embodiment, the at least one extending portionextends circumferentially along said equator line, in the proximalquadrant of the equator line.

According to yet another embodiment, the at least one extending portionextends circumferentially along said equator line, in the distalquadrant of the equator line.

According to yet another embodiment, two extending portions extendscircumferentially along said equator line, in the distal and proximalquadrant thereof.

According to yet another embodiment, the at least one extending portionextends circumferentially along said equator line, in the proximal anddorsal quadrant thereof.

According to yet another embodiment, the at least one extending portionextends circumferentially along said equator line, in the distal anddorsal quadrant thereof.

According to yet another embodiment, the at least one extending portionextends circumferentially along said equator line, in the distal, dorsaland proximal quadrant thereof.

According to yet another embodiment, the at least one first portion ofsaid medical device is an extending portion, extending beyond saidcircular equator line, and at least a second portion is a portion notextending beyond said circular equator line, wherein said second portioncircumferentially extends along at least ¼ of said circular equatorline.

According to yet another embodiment at least a first portion of saidmedical device is an extending portion, extending beyond said circularequator line, and at least a second portion is a portion not extendingbeyond said circular equator line, wherein said second portioncircumferentially extends along at least ⅓ of said circular equatorline.

According to yet another embodiment at least one first portion of themedical device is an extending portion, extending beyond said circularequator line, and at least a second portion is a portion not extendingbeyond said circular equator line, wherein said second portioncircumferentially extends along at least ½ of said circular equatorline.

According to yet another embodiment, at least a first portion of saidmedical device is an extending portion, extending beyond said circularequator line, and at least a second portion is a portion not extendingbeyond said circular equator line, wherein said first portioncircumferentially extends along at least ¼ of said circular equatorline.

According to yet another embodiment, the at least a first portion ofsaid medical device is an extending portion, extending beyond saidcircular equator line, and at least a second portion is a portion notextending beyond said circular equator line, wherein said first portioncircumferentially extends along at least ⅓ of said circular equatorline.

According to yet another embodiment, at least a first portion of themedical device is an extending portion, extending beyond said circularequator line, and at least a second portion is a portion not extendingbeyond said circular equator line, wherein said first portioncircumferentially extends along at least ½ of said circular equatorline.

According to yet another embodiment, at least a first portion of saidmedical device is an extending portion, extending beyond said circularequator line, and at least a second portion is a portion not extendingbeyond said circular equator line, wherein said first portioncircumferentially extends along at least 1/10 of said circular equatorline.

According to another embodiment of the medical device, at least a firstportion of the medical device is an extending portion, extending beyondsaid circular equator line, and at least a second portion is a portionnot extending beyond said circular equator line. The first portioncircumferentially extends along at least 1/10 of said circular equatorline, and the second portion circumferentially extends along at least ¼of said circular equator line.

According to another embodiment, the medical device comprises at leasttwo first portions of said medical device being extending portions,extending beyond said circular equator line, and at least a secondportion being a portion not extending beyond said circular equator line.The first portions each circumferentially extends along at least 1/10 ofsaid circular equator line, and the second portion circumferentiallyextends along at least ¼ of said circular equator line.

According to another embodiment at least two first portions of saidmedical device are extending portions, extending beyond said circularequator line, wherein one of said extending portions extends furtherthan the other extending portion.

According to another embodiment, the medical device further comprisestwo second portions not extending beyond said circular equator line,wherein said two first extending portions circumferentially extendsalong said equator line between said two second portions.

According to yet another embodiment, the medical device furthercomprises at least one hole, wherein said at least one hole is adaptedto receive a fixating member, for fixating said medical device to thepelvic bone.

The hole could be adapted to receive a screw for fixating said medicaldevice to the pelvis.

According to yet another embodiment, the medical device comprises atleast one extending portion adapted to clasp the caput femur, or aprosthetic caput femur, for restraining said caput femur, or prostheticcaput femur in said medical device, and wherein said medical device isadapted to release the caput femur or prosthetic caput femur from saidmedical device when a predetermined strain is placed on said medicaldevice.

According to another embodiment, the extending portion, when implanted,is adapted to be placed such as to restrict the motion range of the hipjoint, and wherein said extending portion is adapted to be placed suchthat adduction is restricted more degrees than flexion.

According to yet another embodiment, the extending portion, whenimplanted, is adapted to be placed such as to restrict the motion rangeof the hip joint, and wherein said extending portion is adapted to beplaced such that abduction is restricted more degrees than flexion.

According to yet another embodiment, the extending portion, whenimplanted, is adapted to be placed such as to restrict the motion rangeof the hip joint, and wherein said extending portion is adapted to beplaced such that adduction is restricted more degrees than extension.

In any of the embodiments, the extending portion, when implanted, isadapted to be placed such as to restrict the motion range of the hipjoint, and wherein said extending portion is adapted to be placed suchthat abduction is restricted more degrees than extension.

According to one embodiment, the medical device comprises at least oneof extending portion, when implanted, adapted to be placed such as torestrict the motion range of the hip joint. The extending portion isadapted to be placed or shaped such that at least one of adduction,abduction, flexion, extension, a combination of flexion and adduction orabduction, a combination of extension and adduction or abduction,rotation in, rotation out, and any combination of rotation in or out andthe other described movements, is restricted more degrees from maximalmovement than any of the other.

According to one embodiment, the prosthetic caput femur is ball shapedand adapted to be at least partly placed inside said inner surface,being bowl shaped. The inner surface comprises an equator line, beingthe largest circular circumference of said inner surface. The at leastone extending portion of the inner surface passes beyond the equatorline, such that the end portion of a contacting portion of the innersurface, the most distal portion of the inner surface is adapted tocontact the prosthetic caput femur, when the inner surface is placedsymmetrically onto the prosthetic caput femur, forms a circularextension line parallel to said equator line having a smallercircumference than said equator line. The at least one extending portionis constructed according to at least one of the following alternatives;a) circumferentially extending discontinuously along said equator linehaving enough circumferential distance lacking any extending portion andb) extending with different distal extension in different extendingportions or part of such portion of said circumferential extension.

According to yet another embodiment, the said inner surface comprises anequator line, being the largest circular circumference of said innersurface, the at least one extending portion of the inner surface passesbeyond the equator line, such that the end portion of a contactingportion of said inner surface. The most distal portion of the innersurface adapted to contact a prosthetic caput femur, when the innersurface is placed symmetrically onto the prosthetic caput femur, forms acircular extension line parallel to said equator line having a smallercircumference than said equator line, and the at least one extendingportion extends with different distal extension over the circumferentialextension, thus adapted to restrict movements clearly different indifferent directions of movement, due to different distal extension ofdifferent extending portions in said circumferential extension.

According to any of the embodiments the said inner surface couldcomprise an equator line, being the largest circular circumference ofsaid inner surface. At least one extending portion of the inner surfacecould pass beyond the equator line, such that the end portion of acontacting portion of said inner surface, the most distal portion ofsaid inner surface adapted to contact a prosthetic caput femur, when theinner surface is placed symmetrically onto the prosthetic caput femur,forms a circular extension line parallel to said equator line having asmaller circumference than said equator line, and part of said at leastone extending portion extends with different distal extension over thecircumferential extension, thus adapted to restrict movements clearlydifferent in different directions of movement, due to different distalextension of different part of such extending portion in saidcircumferential extension.

According to yet another embodiment the medical device comprises alocking member for locking an artificial replacement of an acetabulum ina hip joint to clasp a caput femur or an artificial replacementtherefore, when implanted in a hip joint of a patient, wherein saidlocking member is adapted to in situ assist in the fixation of themedical device. The inner surface comprises an equator line, being thelargest circular circumference of said inner surface. At least oneextending portion of the inner surface passes beyond the equator line,such that the end portion of the contacting portion of the innersurface. The most distal portion of the inner surface is adapted tocontact a caput femur or prosthetic caput femur, when the inner surfaceis placed symmetrically onto the prosthetic caput femur, forms acircular extension line parallel to said equator line having a smallercircumference than said equator line. The locking member is adapted tolock the caput femur or prosthetic caput femur such that the caput femuror prosthetic caput femur remains clasped and restrained in the innersurface, and the locking member is adapted to lock the at least oneextension portion, when implanted, having at least the end portion ofthe extension portion radially fixed within said circular extensionline.

According to another embodiment, the locking member is adapted to lockin at least a first and second locking position.

According to yet another embodiment, the locking member is adapted tolock in at least a first and a second locking position. The lockingmember is adapted to; in said first locking position, lock an artificialcaput femur surface having at least one extending portion, to a firstsize caput and/or collum femur, and in said second locking position,lock said artificial caput femur surface, to a second smaller size caputfemur and/or collum femur.

According to yet another embodiment, the hip joint has a collum femur,having a first axial distribution leading to a caput femur, wherein saidcollum femur is placed distal to the caput femur, a center axis of thecollum and caput femur in line with the first axial distribution beingthe caput femur center axis. The caput femur has a substantially ballshaped configuration with an outer maximum radius perpendicular to thecaput femur center axis, the caput femur being placed in a bowl shapedacetabulum, having an opening, wherein the bowl shaped acetabulum has asecond axial distribution with an acetabulum center axis from the centerof the bottom of the acetabulum bowl and following the center of thebowl towards the center of the opening of the bowl, towards the caputfemur. The acetabulum bowl has an inner maximum radius perpendicular tothe acetabulum center axis, wherein the caput femur center axis is inline/aligned with the acetabulum center axis, in a special centeredposition, when the caput femur is placed; aligned, centered andsymmetrical in the acetabulum bowl in the hip joint, the aligned centeraxis is defined as the hip joint center axis, wherein the caput femurand the acetabulum has one hip joint surface each, placed towards andcontacting each other, wherein the hip joint surfaces carrying weight inthe hip joint are the weight carrying surfaces, wherein the outermaximum radius of the caput femur is forming a circular extending,maximum caput femur radius circle, extending perpendicular to the hipjoint center axis, defining a maximum caput femur radius cross-sectionperpendicular to the hip joint center axis, wherein said medical devicecomprises at least one artificial hip joint surface, adapted to at leastpartly replace at least one of the hip joint surfaces, said artificialhip joint surface at least partly being hollow and having an inner andouter surface, wherein said artificial hip joint surface has anartificial hip joint surface center axis aligned with the hip jointcenter axis when the hip joint is placed in the special centeredposition, when at least one of said artificial hip joint surfaces isimplanted in the hip joint, with the caput femur or an artificial caputfemur surface placed; aligned, centered and symmetrical in theacetabulum bowl or an artificial acetabulum surface in the hip joint,wherein said medical device comprises a central part and a surroundingpart, the central part being aligned with the artificial hip jointsurface center axis and the surrounding part surrounding the surface ofthe caput femur or an artificial caput femur surface not including thecentral part, wherein the caput femur or an artificial caput femursurface, has a maximum caput femur radius cross-section, in which theouter maximum radius of the caput femur or said artificial caput femursurface is forming a circular extending maximum caput femur orartificial caput femur radius circle, extending perpendicular to the hipjoint center axis, defining the maximum caput femur radius cross-sectionperpendicular to the hip joint center axis or perpendicular to saidartificial hip joint surface center axis, when the hip joint is placedin said special centered position, wherein the surrounding part of saidat least one artificial hip joint surface comprises at least one firstextending portion of the artificial hip joint surface for extending indistal direction at least partly beyond the maximum caput femur radiuscross-section, when the hip joint is placed in said special centeredposition, when at least one of the artificial hip joint surfaces isimplanted in the hip joint, wherein said at least one first beyond partis adapted to have a closest perpendicular distance to said artificialhip joint surface center axis, being smaller than an inner maximumdistance, extending perpendicularly from said artificial hip jointsurface center axis to said inner surface of said artificial hip jointsurface, when the hip joint is placed in the above mentioned specialcentered position and said artificial hip joint surface is placed in afunctional position in the hip joint, thus adapted to create andcreating a more stable position of said artificial hip joint surfacewhen mounted in the hip joint.

According to yet another embodiment, the hip joint has a caput femur hipjoint surface partly being the contacting surface of the hip joint, thehip joint further having a collum femur, having a first axialdistribution leading to a caput femur, wherein a center axis of thefirst axial distribution of the collum femur and the caput femur, beingthe caput femur center axis, wherein the collum femur is placed moredistal than caput femur. The medical device comprises an artificialcaput femur surface being hollow, having a major opening adapted to bedirected towards the caput femur or a surgically modified caput femur,wherein said artificial caput femur surface is adapted to replace acaput femur hip joint surface. The artificial caput femur surfacefurther having; a medical device caput center axis passing through saidmajor opening, being aligned with the caput femur center axis, when saidmedical device is implanted in a functional position in the hip joint,wherein said medical device comprises a central part and a surroundingpart, the central part being aligned with the medical device center axisand the surrounding part surrounding the surface of the caput femur orthe surgically modified caput femur not including the central part, andwherein said medical device further comprising an inner surface adaptedto have a first distal distance extending perpendicularly from saidmedical device caput center axis to said inner surface of thesurrounding part of said artificial caput femur surface, said firstdistal distance being shorter than a second proximal distance extendingperpendicularly from said medical device caput center axis to said innersurface of said artificial caput femur surface, said second proximaldistance extending from a more proximal position on said medical devicecaput center axis than said first distal distance, being the secondproximal distance, when said artificial caput femur surface is implantedin said functional position in the hip joint. According to yet anotherembodiment, the hip joint has an acetabulum, being a bowl shapedcontacting surface of the hip joint comprising a substantially circularmajor opening in distal direction of the acetabulum in the hip joint anda bottom center point in said bowl shaped acetabulum proximally in thehip joint, wherein an acetabulum center axis extends from the bottompoint through the center point of the substantially circular opening,wherein the acetabulum has a weight carrying surface contacting a ballshaped caput femur located in the acetabulum bowl in the hip joint,wherein the caput femur is connected to the collum femur, and the collumfemur has a center axis aligned with a caput femur center axis, wherein;said medical device comprises an artificial acetabulum surface adaptedto replace the weight carrying surface of the acetabulum, wherein saidartificial acetabulum surface is hollow and has a major acetabulumopening adapted to be directed towards the caput femur or an artificialreplacement of at least the surface of the caput femur, wherein saidartificial acetabulum surface is adapted to receive a caput femur or anartificial replacement of at least the surface of the caput femur, insaid hollow artificial acetabulum surface, when implanted in the hipjoint, said artificial acetabulum surface having; a medical deviceacetabulum center axis, adapted to be aligned with the acetabulum centeraxis, when said artificial acetabulum surface is placed in the hipjoint, and an inner surface adapted to have a first distal distanceextending perpendicularly from said medical device acetabulum centeraxis, to said inner surface of said artificial acetabulum surface, saidfirst distal distance being shorter than a second proximal distanceextending perpendicularly from said medical device acetabulum centeraxis to said inner surface of said artificial acetabulum surface, saidsecond proximal distance extending from a more proximal position on saidmedical device acetabulum center axis than said first distal distance,when said artificial acetabulum surface is implanted functionally in thehip joint, wherein said artificial acetabulum surface is adapted toreceive in the hollow artificial acetabulum surface the caput femur oran artificial replacement of at least the surface of the caput femur,when implanted in the hip joint, for achieving a functional hip joint.

The medical device could have at least one of extending portion adaptedto have at least one of its shape or position such that the restrictionof movement range of the hip joint, in degrees from maximal movement, isrestricted more in at least one predefined direction than in any otherdirection, when implanted.

A method using any medical device according to any of the precedingclaims is further provided. The method comprises the steps of cuttingthe skin in the hip region dissecting the hip joint implanting themedical device in the hip joint of a patient, fixating the device to thepelvic bone of the patient, and wherein said medical device comprises aninner and an outer surface, having a contacting portion of said innersurface being spherical and bowl shaped facing the inner surface to thecenter of the hip joint having at least one extending portion, extendinga contacting portion for contacting the caput femur or a prostheticreplacement therefor, placing a caput femur or a prosthetic replacementtherefor having a spherical portion, such that said extending contactingportion of said inner surface is clasping said spherical portion of saidcaput femur, or a prosthetic replacement therefore, such that said caputfemur, or a prosthetic replacement therefore is restrained in said bowlshaped inner surface.

The method could further comprise the steps of placing said innersurface contacting the surface of the caput femur or artificialreplacement therefor, the surface of the caput femur or artificialreplacement therefor comprising an equator line being the largestcircular circumference of said surface, placing and passing with said atleast one extending portion beyond said equator line, such that the endportion of said contacting portion of said inner surface forms acircular extension line having a parallel smaller circumference thansaid equator line, the end portion being the most distal portion of theinner surface being in contact with said caput femur or artificialreplacement therefore, when said caput femur or artificial replacementtherefore is placed symmetrically in said inner surface, and whereinsaid at least one extending portion is extending circumferentiallydiscontinuously along said equator line, such that a portion of saidcollum femur or prosthetic replacement therefor can be placed betweensaid extension line and said equator line.

The method could further comprise the step of mounting the at least oneextending portion according to at least one of the followingalternatives: a) extending circumferentially discontinuously along saidequator line having enough circumferential distance lacking anyextending portion and b) extending with different distal extension indifferent extending portions or part of such portion of saidcircumferential extension.

According to yet another embodiment the medical device could comprise alocking member for locking an artificial replacement of an acetabulum ina hip joint to clasp a caput femur or an artificial replacementtherefor, when implanted in a hip joint of a patient. The locking membercould be adapted to in situ assist in the fixation of the medicaldevice. The artificial acetabulum could comprise an inner surfacecomprising an equator line, being the largest circular circumference ofsaid inner surface, wherein at least one extending portion of said innersurface passes beyond said equator line, such that the end portion of acontacting portion of said inner surface, the most distal portion ofsaid inner surface adapted to contact a caput femur or artificial caputfemur forms a circular extension line parallel to said equator linehaving a smaller circumference than said equator line, when the innersurface is placed symmetrically onto the prosthetic caput femur. Themethod could comprise the following steps: cutting the skin in the hipregion, dissecting the hip joint, implanting the medical device in a hipjoint of a patient, fixating the artificial replacement of an acetabulumto the pelvic bone of the patient, comprising an inner and an outersurface, having a contacting portion of said inner surface beingspherical and bowl shaped, facing the inner surface to the center of thehip joint having at least one extending portion, extending a contactingportion for contacting the caput femur or a prosthetic replacementtherefor, placing a caput femur or an artificial replacement thereforehaving a spherical portion, such that said extending contacting portionof said inner surface is clasping said spherical portion of said caputfemur, or an artificial replacement therefore, placing said lockingmember such that said caput femur, or artificial replacement therefor isrestrained in said bowl shaped inner surface, and locking said caputfemur or artificial caput femur in said clasped and restrained positionin said inner surface, by fixating radially at least the end portion ofthe at least one extension portion within said circular extension line.

Please note that any embodiment or part of embodiment, feature, method,associated system, part of system described herein or in the associatedfigures may be combined in any way.

BRIEF DESCRIPTION OF DRAWINGS

The invention is now described, by way of example, with reference to theaccompanying drawings, in which

FIG. 1 a shows pelvis in a frontal view,

FIG. 1 b shows pelvis in a frontal view,

FIG. 1 c shows the hip joint in section,

FIG. 2 a shows pelvis in a lateral view,

FIG. 2 b shows pelvis in a lateral view,

FIG. 2 c shows pelvis in a perspective view from below,

FIG. 2 d shows pelvis in a perspective view from below,

FIG. 2 e shows the acetabulum, schematically,

FIG. 2 f shows the acetabulum, schematically,

FIG. 3 shows the pelvis in a lateral view,

FIG. 4 shows the medical device according to one embodiment, in aperspective view,

FIG. 5 shows the medical device according to one embodiment, whenfixated to the pelvic bone,

FIG. 6 a shows pelvis in a frontal view, when medical device accordingto two embodiments have been implanted,

FIG. 6 b shows pelvis in a frontal view, when medical device accordingto two further embodiments have been implanted,

FIG. 7 shows pelvis in a frontal view, when medical device according totwo embodiments have been implanted,

FIG. 8 shows a medical device according to one embodiment, when placedon a prosthetic caput femur fixated in the femoral bone.

FIG. 9 a shows pelvis in a lateral view, when the medical device isimplanted,

FIG. 9 b shows pelvis in a lateral view, when the medical device isimplanted,

FIG. 10 shows pelvis in a lateral view, when the medical device isimplanted,

FIG. 11 shows pelvis in a lateral view, when the medical device isimplanted,

FIG. 12 shows pelvis in a lateral view, when the medical device isimplanted,

FIG. 13 shows the medical device according to yet another embodiment,

FIG. 14 a shows the medical device according to one embodiment with twoextending portions,

FIG. 14 b shows the medical device according to one embodiment withthree extending portions,

FIG. 14 c shows the medical device according to one embodiment withthree extending portions,

FIG. 14 d shows the medical device according to one embodiment with fourextending portions,

FIG. 14 e shows the medical device according to one embodiment with twoextending portions,

FIG. 14 f shows the medical device according to one embodiment withthree extending portions,

FIG. 15 a shows the hip joint in section when a medical device isimplanted, in its first state,

FIG. 15 a shows the hip joint in section when a medical device isimplanted, in its second state,

FIG. 16 shows the hip joint in section when a medical device isimplanted, in its first state,

FIG. 17 shows the hip joint in section when a medical device isimplanted, in its second state,

FIG. 18 shows the medical device in section, when in its first state,

FIG. 19 shows the hip joint in section when a medical device isimplanted, in its first state,

FIG. 20 shows the hip joint in section when a medical device isimplanted, in it second state,

FIG. 21 shows the hip joint in section when a medical device isimplanted, in its first state,

FIG. 22 shows the hip joint in section when a medical device isimplanted, in it second state,

FIG. 23 a shows the hip joint in section when a medical device isimplanted, in its first state,

FIG. 23 b shows a medical device in section when in it first state,

FIG. 24 a shows the hip joint in section when a medical device isimplanted, in its second state,

FIG. 24 b shows a medical device in section when in its second state,

FIG. 25 shows the hip joint in section when a medical device isimplanted, in its first state,

FIG. 26 shows the hip joint in section when a medical device isimplanted, in its second state,

FIG. 27 shows the hip joint in section when a medical device isimplanted, in its first state,

FIG. 28 shows the hip joint in section when a medical device isimplanted, in it second state,

FIG. 29 shows the hip joint in section when a medical device isimplanted, in it first state,

FIG. 30 shows the hip joint in section when a medical device isimplanted, in it second state,

FIG. 31 shows the hip joint in section when a medical device isimplanted, in it first state,

FIG. 32 shows the hip joint in section when a medical device isimplanted, in it second state,

FIG. 33 shows the hip joint in section when a medical device isimplanted, in it first state,

FIG. 34 shows the hip joint in section when a medical device isimplanted, in it first state,

FIG. 35 shows the hip joint in section when a medical device isimplanted, in its second state.

DETAILED DESCRIPTION

The hip joint is a synovial ball and socket joint which permits a largemotion range for allowing a plurality of different movements of thelower limb. From a neutral position the following movements of the hipjoint are normally possible: Lateral or external rotation, 30° with thehip extended, 50° with the hip flexed, medial or internal rotation 40°,extension or retroversion 20°, flexion or anteversion 140°, abduction50° with hip extended, 80° with hip flexed, adduction 30° with hipextended, 20° with hip flexed.

When replacing the natural hip joint with a prosthetic hip joint, thedepth of the prosthetic acetabulum will affect the motion range, thedeeper the acetabulum bowl is made the more restrictive it is to themotion range. A deeper bowl has the advantage of reducing the risk ofhip joint luxation, the risk of which is a major drawback withprosthetic hips of today.

The anatomy of the hip joint and its surroundings is further disclosedin: Marieb et al., Human Anatomy, 2003, Benjamin Cummings, SanFrancisco, pages 195-202 and in Moore et al., Clinically orientedanatomy,1999, Lippincott; Williams & Wilkins, Baltimore, pages 501-653,both hereby incorporated by reference.

Centrally in the body should herein be understood as a point ofreference located at the intersection of the Median plane and theCoronal plane and in the center part of the heart along a longitudinalaxis (Caudal-Cranial). Proximal and distal are direction or locationterms used in relation to said point centrally in the body and hence adistal point is a point farther away from the central point in relationa proximal point of the same structure. Any plane disclosed herein is tobe understood as having infinite extension. Other anatomical terms usedherein are further described in Moore et al., Clinically orientedanatomy,1999, Lippincott, Williams & Wilkins, Baltimore, pages 2-10,which is hereby incorporated by reference.

Functional hip movements are to be understood as movements of the hipthat at least partly correspond to the natural movements of the hip. Onsome occasions the natural movements of the hip joint might be somewhatlimited or altered after hip joint surgery, which makes the functionalhip movements of a hip joint with prosthetic surfaces somewhat differentthan the functional hip movements of a natural hip joint.

Everyday activities is to be understood as activities which are notconnected to any extreme movements, such that some physical sportsrequire. For example, everyday activities comprise: walking, sitting,cycling etc.

The functional position of an implantable medical device or prosthesisis the position in which the hip joint can perform functional hipmovements. The final position is to be understood as a functionalposition in which the medical device needs no further position change tofunction.

Arthroscopy is to be understood as key hole surgery performed in ajoint, since the arthroscopic procedure could be performed in theabdomen of the patient some of the steps of this arthroscopic procedureis more laparoscopic, however for the purpose of this invention the twoterms arthroscopy and laparoscopy is used synonymously and for thepurpose of this invention the main purpose of these methods are is thatthey are minimally invasive.

Elastic deformation is when a material deforms under stress (e.g.external forces), but returns to its original shape when the stress isremoved. A more elastic material is to be understood as a materialhaving a lower modulus of elasticity. The elastic modulus of an objectis defined as the slope of its stress-strain curve in the elasticdeformation region. The elastic modulus is calculated as stress/strain,where stress is the force causing the deformation, divided by the areato which the force is applied; and strain is the ratio of the changecaused by the stress.

Elasticity is to be understood as a materials ability to deform in anelastic way.

Stiffness is to be understood as the resistance of an elastic body todeformation by an applied force.

Biocompatible material is to be understood as being a material with lowlevel of immune response. Biocompatible materials are sometimes alsoreferred to as biomaterials. Analogous is biocompatible metals abiocompatible metal with low immune response such as titanium ortantalum. The biocompatible metal could also be a biocompatible alloycomprising at least one biocompatible metal.

Form fitting is to be understood as an element having a part or sectionwhich is adapted to enable a mechanical connection of said element to atleast one other element using said part or section. Form fittedstructure is a structure of an element which enables form fitting.

In the following a detailed description of embodiments of the presentinvention will be given. In the drawing figures, like reference numeralsdesignate identical or corresponding elements throughout the severalfigures. It will be appreciated that these figures are for illustrationonly and are not in any way restricting the scope of the invention.Thus, any references to direction, such as “up” or “down”, are onlyreferring to the directions shown in the figures. Also, any dimensionsetc. shown in the figures are for illustration purposes.

FIG. 1 shows the pelvis in a frontal view. Pelvis comprises the rightand left hip bone making up the pelvic bone, in turn comprising theSacrum 1803, Ilium 1802, Pubis 1804 and Ischium 1801. The hip jointhouses the right and left acetabulum 8 a,b placed laterally and distallyin the pelvis. The acetabulum 8 a,b being a spherically shaped cavity inthe hip bones making up one of the parts of the hip joint, theacetabulum 8 a,b being adapted to house the caput femur 5, being theproximal portion of the femoral bone 7 having a spherical contactingsurface adapted to be placed in the acetabulum 8 a,b and thus creatingthe operable hip joint. The pelvis has a right-left axis X extendingsubstantially from the bottom of the left acetabulum 8 a to the bottomof the right acetabulum 8 b, the pelvis further having a caudal-cranialaxis Y extending perpendicular to said right-left axis, centrally andsubstantially along the length of the patient, passing the dorsalportions of the pubic symphysis 1805 and substantially following thespinal cord 1806, intersecting the left-right axis X.

FIG. 1 b shows the pelvis in a frontal view disclosing a second,displaced coordinate system. The second displaced coordinate system hasits origin O′ in the bottom of the acetabulum bowl 8 a. The axis X and Yhave, in a frontal view, been rotated the angle β, creating the axis X′and Y′. The axis X′, being aligned with the caput and collum femurcenter axis when the hip joint is in its base position, when the patientis standing up or lying down. In said base position the axis X′ goesthrough a point 0′ being the bottom of the acetabulum bowl, and a centerpoint CP, being a point in the center of a circle defined by the edgesof the acetabulum bowl, and further trough the top of the caput femur 5and following inside of the collum femur 6, aligned with the collumfemur 6. The axis Y is perpendicular to the axis X′ and goes through theorigin O′ in the bottom of the acetabulum bowl 8 a, parallel to a planedefined by the circle defined by the edges of the acetabulum bowl 8 a.

FIG. 1 c shows the right pelvic bone in section disclosing the second,displaced coordinate system. The origin O′ is in the bottom of theacetabulum bowl 8. The axis X′ is aligned with the caput 5 and collum 6femur center axis, when the hip joint is in its base position when thepatient is standing up or lying down with extended leg. In said baseposition the axis X′ is goes through a point O′ being the bottom of theacetabulum bowl 8, and a center point CP, being a point in the center ofa circle defined by the edges of the acetabulum bowl 8, and furthertrough the top of the caput femur 5′ and following inside of the collumfemur 6, aligned with the collum femur 6. The axis Y′ is perpendicularto the axis X′, goes through the origin O′ in the bottom of theacetabulum bowl 8, parallel to the plane PC defined by the circledefined by the edges of the acetabulum bowl 8.

FIG. 2 a shows the pelvis in a lateral view, thus displaying theposterior side of Ilimu 1802, the anterior side of Ichum 1801, theanterior side of Pubis 1804, and Sacrum 1803 in a strict lateral view.The pelvis has furthermore a dorsoventral axis Z being perpendicular tothe caudal-cranial axis Y and the right-left axis X shown in FIG. 1, andintersecting them both creating a common origin O for the three axisX,Y,Z. The dorsoventral axis Z and the caudal-cranial axis Y thus beingoriented such that a horizontal pelvis plane PXZ extends from thedorsoventral axis Z, and a coronal plane PXY extends from thecaudal-cranial axis Y.

FIG. 2 b shows the pelvis in a plane view from the side and slightlyfrom below, in the direction of the axis X′ (further disclosed withreference to FIGS. 1 b and 1 c. The view of FIG. 2 b displaying the axisY′ and Z′ with origin O′ in the bottom of the acetabulum bowl 8 makingup the acetabulum coordinate system. The axis Y′, Z′, in this planeview, dividing the acetabulum bowl 8 into four quadrants theproximal-frontal quadrant 1807, the distal-frontal quadrant 1808, thedistal-dorsal quadrant 1809 and the proximal-dorsal quadrant 1810.

FIG. 2 c shows the pelvis in a perspective view from below and slightlyfrom the front, displaying the right-left axis X passing through thecenter of the right and left acetabulum 8. The right-left axis X isperpendicular to the dorsoventral axis Z which also is perpendicular tothe caudal-cranial axis Y. The coronal plane PXY extends from thedorsoventral axis Y, and the horizontal pelvis plane PXZ extends fromthe dorsoventral axis Z, thus being perpendicular to the coronal planePXY.

FIG. 2 d shows the coordinate system X,Y,Z and planes PXY, PXZ of FIG. 2c and the second, displaced, coordinate system X′,Y′,Z′, being thecoordinate system of the acetabulum 8, also shown in FIG. 2 b. The axisof the coordinate system of the acetabulum X′, Y′, Z′ having theirorigin O′ in the bottom of the acetabulum bowl 8. FIG. 2 d furtherdiscloses the vertical acetabulum plane PX′Y′ and the horizontalacetabulum plane PX′Z′, PX′Y′ being defined by the axis X′,Y′ and PX′Z′being defined by the axis X′,Z′. The planes PX′Y′ and PX′Z′ dividing theacetabulum bowl 8 into four quadrant, the proximal-frontal quadrant1807, the distal-frontal quadrant 1808, the distal-dorsal quadrant 1809and the proximal-dorsal quadrant 1810, in accordance with what ispreviously disclosed, with reference to FIG. 2 b. FIG. 2 d further showsthe location of foramen obturatum 1871.

FIG. 2 e shows, schematically how the acetabulum coordinate systemX,Y′,Z′ relates to the hemisphere defined by the acetabulum bowl 8.

FIG. 2 f shows, schematically, how the vertical acetabulum plane PX′Y′,and the horizontal acetabulum plane PX′Z′ divides the acetabulum 8 intofour quadrant; the proximal-frontal quadrant 1807, the distal-frontalquadrant 1808, the distal-dorsal quadrant 1809 and the proximal-dorsalquadrant 1810, in accordance with the previously disclosed, withreference to FIGS. 2 b and 2 d.

FIG. 2 g shows the axis and planes disclosed with reference to FIG. 2 dwith the pelvis removed such that the coordinate systems should appearclearer.

FIG. 3 shows pelvis in the same view as FIG. 2 b. Here the vertical andhorizontal acetabulum planes PX′Y′ and PX′Z′ (further disclosed withreference to FIG. 2 d) are shown in a strict plane view. Two furtherplanes PX″Y″ is introduced in FIG. 3, which planes are rotated an angleα of 45° clockwise. The planes PX″Y″ and PX″Z″, in accordance with theplanes PX′Y′ and PX′Z′ divides the acetabulum bowl into four differentquadrant, being a proximal quadrant 1811, a frontal quadrant 1812, adistal quadrant 1813 and a dorsal quadrant 1814.

FIG. 4 shows a medical device for implantation in a hip joint of apatient. The medical device is adapted to be fixated to the pelvic boneof the patient for example by means of an adhesive, such as bone cement,or mechanical fixating members, such as orthopedic screws. The medicaldevice comprises an inner 1827 and an outer 1828 surface. A contactingportion of the inner surface 1827 is spherical and faces the center ofthe hip joint, when the medical device is implanted. The inside of themedical device is adapted to receive a caput femur or a prostheticreplacement therefor having a spherical portion, and the sphericalcontacting portion of the inner surface 1827 is adapted to be in contactwith a spherical portion of the outer surface of the caput femur or aprosthetic replacement therefor. The medical device, according to theembodiment shown in FIG. 4 comprises two extending portions 1823 a,b,extending the contacting portion of the inner surface 1827′ such thatthe extending portions 1823 a,b clasps the spherical portion of caputfemur or a prosthetic replacement therefor, for restraining thespherical portion in the medical device. The medical device is adaptedto receive the caput femur or a prosthetic replacement therefor, havinga collum femur or prosthetic collum femur fixated to the sphericalportion of the caput femur or prosthetic replacement therefor. The innersurface 1827 comprises an equator line 1821, being the largest circularcircumference of the inner surface. The two extending portions passesbeyond the equator line 1821, such that an end portion 1829 of thecontacting portion, here being of the extending portion 1823 b of theinner surface 1827, forms a circular extension line 1822 placed distalto the equator line 1821, when the medical device is implanted, andhaving a smaller circumference than the equator line 1821; thus adistance 1826 between a center axis P of the medical device and theextension line 1822 is shorter than a distance 1825 between the centeraxis P and the equator line 1821.

FIG. 5 shows the medical device described with reference to FIG. 4 whenimplanted. According to this embodiment the medical device is adapted tobe fixated using orthopedic screws 1830, mechanically fixating themedical device to the pelvic bone 9, by the medical device comprisingholes through which the screws 1830 are placed. In FIG. 5 the contactingportion of the inner surface 1827 has been placed in contact with thespherical portion of a prosthetic caput femur 5 being fixated to aprosthetic collum femur 6, the prosthetic caput 5 and collum 6 femurreplacing the proximal portion of the femoral bone. The two extendingportions 1823 a and 1823 b extending the contacting portion of the innersurface and clasps the spherical portion of the prosthetic caput femur5, for restraining the spherical portion in the medical device. Theinner surface comprising the equator line 1821, and the extendingportions 1823 a,b passing beyond the equator line 1821 and comprisingthe more distal extension line 1822 having a smaller circumference thanthe equator line 1821. The more distal extension line 1822 being placedat a distance D1 from the equator line 1821. According to thisembodiment the extension line 1822 is parallel to the equator line 1821,however this is not necessarily so in other embodiments.

The extension portion 1823 a according to the embodiment shown in FIG. 5extends circumferentially along the equator line, a distance D2. Alonganother portion of the equator line, a distance D3, there are noextending portion, which enables the collum femur 6 to enter the spacebetween the first and second extending portions 1823 a,b which creates alarger movement range of the hip joint.

The extending portions thus extending discontinuously along the equatorline 1821, such that a portion of the collum femur 6 can be placedbetween the extension line 1822 and the equator line 1821.

The extending portion, according to any of the embodiments, adapted toclasp the caput femur or prosthetic replacement therefor for restrainingthe caput femur or prosthetic replacement therefor in the medicaldevice, could further be adapted to release the caput femur orprosthetic replacement therefor when a large enough strain is placed onthe joint. This feature enables the caput femur or prostheticreplacement therefor to be fixedly attached in the medical device innormal use and be released from the medical device e.g. in case of anaccident, thus reducing the risk of damaging the bodily structures, suchas the femoral bone, or the fixations between bodily structures andprosthetic part, such as the fixation between the femoral bone and aprosthetic stem to which the prosthetic collum and caput femur isfixated.

According to one embodiment the extending elements, as for exampledisclosed with reference to FIGS. 1-5, are placed such that theextending elements restrict the motion range minimally, or in ways whichare not limiting the motion range used in everyday life. The hip jointis a synovial ball and socket joint which permit a large motion rangefor allowing a plurality of different movement of the lower limb. From aneutral position the following movements of the hip joint are normallypossible: lateral or external rotation, 30° with the hip extended, 50°with the hip flexed, medial or internal rotation 40°, extension orretroversion 20°, flexion or anteversion 140°, abduction 50° with hipextended, 80° with hip flexed, adduction 30° with hip extended, 20° withhip flexed. In the movement ranges of abduction and adduction the depthof the acetabulum bowl and thus the extending portions does not restrictthe motion range in a critical way since the motion range of the normalhip is restricted in these movements, in normally agile persons, by themuscles, tenors and ligaments surrounding the hip joint.

FIG. 6 a shows a frontal view of pubis and the proximal portions of thefemoral bones 7 when two embodiments of the medical device has beenimplanted in the hip joint. The medical device shown placed on the rightcaput femur 5 a and placed in the right acetabulum 8 a comprises oneextending portion 1823, here placed dorsal to the vertical acetabulumplane PX′Y′, thus only partially limiting abduction in far excess of50°. According to the embodiment shown, the extending portion 1823extends circumferentially along the equator line 1821 about 1/10 of thelength of the equator line 1821, however in other embodiment theextending portion 1823 extends along as much as half of the length ofthe equator line 1821, and in other embodiments the extending portion1823 extends as lithe as about 1/30 of the length of the equator line1821. The medical device shown placed on the left caput femur 5 b andplaced in the left acetabulum 8 b comprises two extending portions 1823a,b, both being placed dorsal the corresponding vertical acetabulumplane PX′Y′ of the left acetabulum (not shown), thus limiting the motionrange of the hip joint in a non restrictive way, in relation to everydayactivities. In both the right and left embodiment the extending portions1823 extends discontinuously along the equator line 1821 thus enablingthe collum femur 6 to partially be placed between the equator line andthe extension line, and in the left embodiment, be placed between theextending portions 1823 a,b thus entering the cavity between theextending portions 1823 a,b.

FIG. 6 b shows a frontal view of pubis and the proximal portions of thefemoral bones 7 when two further embodiments of the medical device havebeen implanted in the hip joint. The medical device shown placed on theright caput femur 5 a and placed in the right acetabulum 8 a comprisesone extending portion 1823, here placed in the proximal quadrant, whichis further disclosed with reference to FIG. 3, thus limiting the motionrange of the hip joint in a non restrictive way, in relation to everydayactivities. According to the embodiment shown, the extending portion1823 extends circumferentially along the equator line 1821 about 1/10 ofthe length of the equator line 1821, however in other embodiments theextending portion 1823 extends along as much as half of the length ofthe equator line 1821, and in other embodiments the extending portion1823 extends as little as about 1/30 of the length of the equator line1821. The medical device shown placed on the left caput femur 5 b andplaced in the left acetabulum 8 b comprises two extending portions 1823a,b, being placed in the proximal and distal quadrant, thus limiting themotion range of the hip joint in a non restrictive way, in relation toeveryday activities.

FIG. 7 shows the pelvis and the proximal portions of the femoral bones 7including the embodiment of FIG. 6 a, with the difference that thenatural caput femur and a portion of the natural collum femur has beenreplaced by a prosthetic caput femur 1833 and a prosthetic collum femur1832. The prosthesis further comprises a prosthetic stem 1831 adapted tobe placed inside and fixated to the femoral bone, either using bonecement or by the surface of the stem being adapted to facilitate thegrowth-in of bone, thus fixating the stem. The prosthetic collum femur1832 could be coordinated with the extending portions 1823 of themedical device for further improving the motion range of the hip joint,or not limiting the natural motion range of the hip joint.

FIG. 8 shows the medical device according to an embodiment in which themedical device comprises two extending portions 1823 a,b. The medicaldevice is placed on a prosthetic collum femur 1832, to which aprosthetic caput femur 1833 is attached. The prosthesis furthercomprises a stem 1831 which is adapted to be fixated inside of thefemoral bone 7. The prosthetic collum femur 1832 is here adapted tofurther improve the motion range of the hip joint, or not limiting thenatural motion range of the hip joint, by the prosthetic collum femur1832 comprising a cavity 1834 in which the extending portions 1823 canbe placed.

FIG. 9 a shows the pelvis in a lateral view, the medical devicecomprises two extending portions 1823 a,b, both extendingcircumferentially along the equator line (as disclosed in for exampleFIG. 5) dorsal to the caudal-cranial axis Y and being adapted to claspthe caput femur or a prosthetic replacement therefor. The extendingportions 1823 a,b extending dorsal to the caudal-cranial axis Y and thusreducing the limiting effect that the extending portions 1823 a,b, haveon the motion range of the hip joint. According to the embodiment shownin FIG. 9 a the extending portion 1823 a placed proximally in theacetabulum extends circumferentially a distance of about ¼ of the lengthof the equator line, and the extending portion 1823 b placed distally inthe acetabulum extends circumferentially a distance of about 1/10 of thelength of the equator line, however it is equally conceivable that thisrelationship is the other way around, or that any of the extendingportions circumferentially extends a distance of as much as half of thelength of the equator line, thus extending the entire distance of theequator line being dorsal to the vertical acetabulum plane PX′Y′, orthat any of the extending portions 1823 a,b extends a distance being aslithe as 1/30 of the distance of the equator line. According to theembodiment shown in FIG. 9 a, the first extending portion 1823 a extendsin distal-lateral direction from the acetabulum, and the secondextending portion 1823 b extends medially towards foramen obturatum.

FIG. 9 b shows the pelvis in a lateral view, the medical devicecomprises two extending portions 1823 a,b, the two extending portions1823 a,b extends in the proximal quadrant 1811 and the distal quadrant1813, respectively.

There are multiple ways in which the extending portions 1823 can beadapted to reduce the effects that the extensions have on the motionrange of the hip joint.

FIG. 10 shows the pelvis in a lateral view, the medical device showncomprises one extending portion 1823 extending and being adapted toclasp the caput femur, or a prosthetic replacement therefor. Theextending portion 1823 extends circumferentially along the equator linewithin the proximal quadrant 1811, which is further disclosed withreference to FIG. 3. According to the embodiment shown in FIG. 10, theextending portion 1823 extends in distal-lateral direction from theacetabulum.

FIG. 11 shows the pelvis in a lateral view, the medical device showncomprises a continuously extending portion 1823 with two extendingportions 1823 a and 1823 b extending further in relation to the averageextension of the extending portion. The entire extending portion isplaced in the proximal, distal and dorsal quadrants and the extendingportions 1823 a,b extending further than the average extension of theextending portion 1823 extends in the proximal and distal quadrant.

FIG. 12 shows the pelvis in a lateral view, the medical device showncomprises four extending portions 1823 a,b,c,d, wherein the first 1823 aand second 1823 b extending portions extends in the proximal and distalquadrant, respectively, thus the first extending portion 1823 aextending in distal-lateral direction from the acetabulum, and thesecond extending portion 1823 b extending medially towards foramenobturatum. The third extending portion 1823 c extending in the frontalquadrant 1812, out from the acetabulum in dorsal direction, extends lessthan the first and second extending portion, since extending portions1823 c in the frontal quadrant is more limiting to the normal motionrange of the hip joint. The fourth extending portion 1823 d extends inthe dorsal quadrant in accordance with the third extending portion 1823c do not extend as far as the first and second extending portions.

FIG. 13 shows an alternative embodiment of the medical device. In thealternative embodiment the medical device comprises a first part 1841adapted to be fixated to the pelvic bone of the patient. The first partcomprises an inner contacting surface adapted to be in movableconnection with an outer contacting surface of a second part 1842. Thesecond part 1842 is rotatably fixated to the first part 1841 by arotatable connecting member 1843. An outer contacting surface of aprosthetic caput femur 1833 is adapted to be placed in contact with theinner surface of the second part 1842 and be movable in multipledirections, thus replicating the natural ball and socket joint of thehip. The second part 1842 comprises two extending portions 1823 a,bextending beyond the equator line 1845 of the second part 1842. Theextending portions 1823 a,b extends longitudinally discontinuously alongthe equator line, thus creating an area between the extending portions,in which area a portion of the prosthetic collum femur can be placed,thus being placed partially between the equator line 1845 and theextension line 1846. The construction shown in FIG. 13 enables thesecond part 1842 to rotate if the collum femur 1832 engages theextending portions 1823 a,b, which are sloped for this purpose. This waythe second part 1842 are always placed such that the collum femur 1832can be placed partially between equator line 1845 and the extension line1846, which creates an optimal range of movement whilst the second partclasps the prosthetic caput femur 1833, and thus restricting the caputfemur 1833 in the second part 1842 of the medical device. According tothe embodiment shown the caput and collum femur is a prosthetic caput1833 and collum 1832 femur, comprising a prosthetic stem 1831 adapted tobe fixated in the femoral bone 7, however, in other embodiment, it isequally conceivable that the natural caput femur is resurfaced andplaced in the second part 1842.

FIG. 14 a shows the medical device 65 in a perspective view from belowaccording to one embodiment. In this embodiment the medical devicecomprises two extending portions 1823 a, b. The medical device 65 isaccording to this embodiment adapted to be fixated to the pelvic bone bymeans of an adhesive which is adapted to be placed in connection withthe adhesive recesses 1870 of the outer surface of the medical device65.

FIG. 14 b shows a medical device similar to the medical device disclosedwith reference to FIG. 14 a, but with the difference that it comprisesthree equally extending portions 1823 a,b,c.

FIG. 14 c shows a medical device similar to the medical device disclosedwith reference to FIG. 14 a, but with the difference that it comprisestwo equally extending portions 1823 a,b and one less extending portion1823 c.

FIG. 14 d shows a medical device similar to the medical device disclosedwith reference to FIG. 14 a, but with the difference that it comprisesfour equally extending portions 1823 a,b,c,d.

FIG. 14 e shows a medical device similar to the medical device disclosedwith reference to FIG. 14 a, but with the difference that the twoextending portions are placed further from each other, and thus beingadapted to be placed in the proximal and distal quadrant, whenimplanted.

FIG. 14 f shows a medical device similar to the medical device disclosedwith reference to FIG. 14 a, but further comprising a less extendingportion 1823 c placed between the first and second extending portions1823 a,b.

The extending portions of the medical device which have been describedcould be made from an elastic material, enabling the extending portionsto pass onto the caput femur.

The extending portions of the medical device, which have been described,could be extending circumferentially a distance such that the materialin the extending portion exerts a significant pressure and thus assistsin the fixation of the medical device to the caput femur. Such acircumferentially extending distance could according to one embodimentbe more that 2 mm and according to another embodiment be more than 5 mm,and according to another embodiment be more than 8 mm, and according toanother embodiment be more than 12 mm. In other embodiments in which themedical device comprises a plurality of extending portions, for examplein embodiment where a first extending portion is less extending than asecond extending portion, it is possible that the less extending portioncircumferentially extends further than the more extending portion, forexample the less extending portion could extend circumferentially adistance of more than 10 mm and the more extending portion could extenda distance of less than 10 mm, or the less extending portion couldextend circumferentially a distance of more than 20 mm and the moreextending portion could extend a distance of less than 20 mm. Accordingto embodiments in which the medical device comprises a plurality ofextending portions extending substantially an equal length, a first oneof the extending portions could be extend circumferentially more that 2mm, and according to another embodiment, more than 5 mm, and accordingto another embodiment, more than 8 mm, and according to anotherembodiment, more than 12 mm, as well as the second extending portionwhich could extend circumferentially more than 2 mm and according toanother embodiment, more than 5 mm, and according to another embodiment,more than 8 mm, and according to another embodiment, more than 12 mm,analogous for a possibly existing third, fourth and so on extendingportion.

FIG. 15 a shows the medical device in an embodiment in which the medicaldevice is fixated to the pelvic bone 9. The medical device comprisesextending portions which in turn serves as releasing members 801adapted, in a first state, to hold the caput femur in the medical deviceand in a second state release the caput femur 5 from the medical device.The releasing member 801 is adapted to change from the first state tothe second state when a pre-determined strain is placed on the releasingmember 801. The strain could be caused by an abnormal movement of thehip joint, e.g. as the result of the patient falling. According to theembodiment shown in FIG. 14 the releasing member 801 comprises anelastic portion comprising elastic material, in the embodiment shownbeing the entire releasing member 801. The releasing member is adaptedto non-invasively be able to change from the first state to the secondstate and from the second state to the first state, when apre-determined strain is placed on the releasing member 801 i.e.

FIG. 15 b shows the hip joint in section when the releasing member 801is in its second state, wherein the releasing member 801 is adapted torelease the caput femur 5 from the medical device placed in the pelvicbone 9. The releasing member 801 has changed from the first state to thesecond state because a pre-determined strain has been placed on thereleasing member 801.

FIG. 16 shows the medical device according to an embodiment where themedical device comprises holding members 802 a,b, adapted to slideagainst the caput femur 5, or a prosthetic replacement therefore. Theholding members are adapted to, in a first state, hold the caput femur5, or a prosthetic replacement therefore, in a second state thereleasing member 801 is adapted to release the caput femur 5, or aprosthetic replacement therefore, from the medical device placed in thepelvic bone 9. The holding members 802 a,b are spring loaded through aspring 803 a,b being placed between a calibration member, being acalibration screw 804 a,b, and the holding members 802 a,b. The forceexerted on the holding members 802 a,b from the spring 803 a,b isadapted to hold the caput femur 5, or a prosthetic replacementtherefore, in the medical device in normal, functional hip jointmovements, but release the caput femur 5, or a prosthetic replacementtherefore, from the medical device when a pre-determined strain isplaced on the releasing member which could be caused by an abnormalmovement of the hip joint, e.g. as the result of the patient falling.The calibration screws 804 a,b enables the pre-determination of thestrain which will cause the holding members 802 a,b to change from beingin a first state to being in a second state.

FIG. 17 shows the releasing members in their second state, when apre-determined strain has been exceeded, preferably being caused by anabnormal movement of the hip joint, e.g. as the result of the patientfalling. The holding members 802 a,b are retracted into sleeves 806 ofthe medical device, thereby compressing the springs 803 a,b. Theretraction of the holding members 802 a,b causes the caput femur 5, or aprosthetic replacement therefore, to be dislocated/luxated from itsposition in the medical device, which, when large strain is placed onthe hip joint and femoral bone 7, reduces the risk of the patientfracturing the femoral bone 7 or the pelvic bone 9. The holding members802 a,b are adapted to non-invasively be able to change from the firststate to the second state and from the second state to the first state,when a pre-determined strain is placed on the holding members 802 a,b.

FIG. 18 shows the medical device in section, with the holding members802, placed in sleeves 806 evenly distributed along the cross-section ofthe medical device, holding the caput femur 5, or a prostheticreplacement therefore, in position in the medical device.

FIG. 19 shows an alternative embodiment of the principle shown in FIGS.16-18, wherein the holding members 802 a,b, comprises ball shapedmembers 805 a,b in contact with the caput femur 5, or a prostheticreplacement therefore, and being adapted to roll against the caput femur5, or a prosthetic replacement therefore, holding the caput femur 5, ora prosthetic replacement therefore, in place in the medical device, bythe holding members 802 a,b exerting force on the caput femur 5, or aprosthetic replacement therefore, through the contact with the springs803 a,b supported by the calibration screws 804 a,b.

FIG. 20 shows the releasing members in their second state, when apre-determined strain has been exceeded, preferably being caused by anabnormal movement of the hip joint, e.g. as the result of the patientfalling. The holding members 802 a,b, comprising the ball shaped members805 a,b, are retracted into sleeves 806 of the Medical device, therebycompressing the springs 803 a,b. The retraction of the holding members802 a,b causes the caput femur 5, or a prosthetic replacement therefore,to be dislocated/luxated from its position in the medical device, which,when large strain is placed on the hip joint and femoral bone 7, reducesthe risk of the patient fracturing the femoral bone 7 or the pelvic bone9. The holding members 802 a,b are adapted to non-invasively be able tochange from the first state to the second state and from the secondstate to the first state, when a pre-determined strain is placed on theholding members 802 a,b, which enables the caput femur 5, or aprosthetic replacement therefore, to be replaced in the medical devicewithout a surgical procedure.

FIG. 21 shows the medical device in an embodiment wherein the releasingmembers 801 comprises a rupture device 807, 808, 809 adapted to fail ata pre-determined strain. According to this embodiment the rupture deviceis a rupture pin 807, 808, 809 comprising a base part 809 a,b fixated tothe medical device and a rupture part 807 a,b attached to the base part809 a,b through a weakened section 808 a,b, in which section the rupturepart 807 a,b is detached from the base part 809 a,b when a predeterminedstrain is placed on the rupture device in contact with the caput femur5, or a prosthetic replacement therefore.

FIG. 22 shows the medical device according to the embodiment of FIG. 21when the rupture device has failed due to a pre-determined strain on therupture device being exceeded. According to one embodiment, (not shown)the rupture parts 807 a,b are secured to the base part through asecurity wire keeping rupture parts 807 a,b in proximity to the basepart 809 a,b even after the failure of the rupture device.

FIG. 23 a shows the medical device according to an embodiment where themedical device comprises a circular sleeve 806, in which an elastic orrupture band 810 is provided. The elastic or rupture band 810 is adaptedto at least partly encircle the ball shaped caput femur 5, or prostheticreplacement therefore. When a pre-determined strain is placed on theelastic or rupture band 810 the circular opening encircling the caputfemur 5, or a prosthetic replacement therefore, is expanded and thecaput femur 5, or a prosthetic replacement therefore, is released fromthe medical device, to which it is held by means of the elastic band610. In embodiments where the medical device comprises a rupture band810 holding the caput femur 5, or a prosthetic replacement therefore, inthe medical device, a weakened portion 811 of the band 810 fails andthus the circular opening encircling the caput femur 5, or a prostheticreplacement therefore, is expanded and the caput femur 5, or aprosthetic replacement therefore, is released from the medical device.In the embodiments where the band 810 is an elastic band 810 it isconceivable that the band 810 comprises an elastic part or section, orthat the entire band 810 is made of an elastic material.

FIG. 23 b shows the medical device in section when the elastic orrupturing band 810, holding the caput femur 5, or a prostheticreplacement therefore, is placed in a circular sleeve 806 in the medicaldevice. An opening or weakened portion 811 is provided perpendicular tothe circumference of the band 810.

FIG. 24 a shows the medical device in a second state where the caputfemur 5, or a prosthetic replacement therefore, is released from theconnection with the medical device, after a pre-determined stain hasbeen placed on the elastic or rupture band 810. As shown in FIG. 24 b,the gap or weakened part has been expanded, thereby allowing the caputfemur, or a prosthetic replacement therefore, 5 to pass through theopening defined by the elastic or rupture band 810. The medical devicecould be adapted to non-invasively be able to change from the firststate to the second state and from the second state to the first state,when a pre-determined strain is placed on the band 810, which enablesthe caput femur 5, or a prosthetic replacement therefore, to be replacedin the medical device without a surgical procedure.

FIG. 25 shows the medical device according to an embodiment where thereleasing member 801 comprises an elastic wing of the medical device,which is assisted by an elastic or rupture band 810 encircling themedical device by enclosing the caput femur 5, or a prostheticreplacement therefore, in the medical device passing beyond the point ofthe caput femur 5, or a prosthetic replacement therefore, having alargest cross-sectional distance. The elastic or rupture band 810 isheld in place to the medical device by means of the band 810 beingplaced in a groove along the circumference of the medical device.However, said groove could be assisted or replaced by an adhesive or amechanical fixation element.

FIG. 26 shows the medical device when in its second state, in which thereleasing member 801 releases the caput femur 5 or a prostheticreplacement therefore, from the medical device. In embodiments when theband 810 is an elastic band 810 it could be expanded, thereby enlargingthe hole through which the caput femur 5, or a prosthetic replacementtherefore, can pass. In embodiments where the band 810 is a ruptureband, the band 810 fails and thereby the caput femur 5, or a prostheticreplacement therefore, is held in place solely by the releasing member801 which is a part of the extending portion adapted to release thecaput femur 5, or a prosthetic replacement therefore, at a pre-definedstrain. The medical device could be adapted to non-invasively be able tochange from the first state to the second state and from the secondstate to the first state, when a pre-determined strain is placed on theband 810 and/or the releasing member 801, which enables the caput femur5, or a prosthetic replacement therefore, to be replaced in the medicaldevice without a surgical procedure.

FIG. 27 shows the hip joint in section according to an embodiment wherethe caput femur 5, or a prosthetic replacement therefore, and collumfemur 6 have been replaced with a prosthetic part 818 fixated to thefemoral bone 7, either with bone cement, or without. The prosthetic part818 comprises a prosthetic caput femur 812 having a cavity 816 in whicha rupture band 813 fixated to a fixation portion 814 of the prostheticcaput femur 812, and a fixating portion 815 of the medical device. Thecavity 816 is adapted to enable the prosthetic caput femur 812 toperform normal functional hip movements inside the medical device. Therupture band 813 is adapted to hold the prosthetic caput femur 812 tothe medical device in a first state, and release the prosthetic caputfemur 812 from the medical device when a pre-determined strain is placedon the rupture band 813.

FIG. 28 shows the embodiment of the medical device according to FIG. 27,in a second state in which the rupture band 813 has failed and therebythe prosthetic caput femur 812 is released from the medical device. Therupture band 813 could be fixated to a fixation portion 814 of theprosthetic caput femur 812, and/or a fixating portion 815 of the medicaldevice using: at least one screw, at least one pin, form fitting,welding, adhesive, pin, wire, a ball mounted into a bowl, a male portionof one part mounted into a female portion of the other part, a keyintroduced into a lock being portions of said parts, band, or othermechanical connecting members. The failing of the rupture band 813 iswhich could be caused by an abnormal movement of the hip joint, e.g. asthe result of the patient falling.

FIG. 29 shows a prosthetic part 818 according to an embodiment where theprosthetic part 818 is fixated to the femoral bone 7 and comprises acaput femur 812 comprising a cavity 816 adapted to enable the hip jointto perform functional hip joint movements while in a first state held tothe medical device using an elastic bend 817 fixated to a fixationportion 814 of the prosthetic caput femur 812, and a fixating portion815 of the medical device, and a releasing member 801 according to theembodiment shown in FIGS. 9 and 10. The combination of the releasingmember 801 and the elastic band 817 is adapted to, in a first state holdthe prosthetic part 818 to the medical device, and in a second staterelease the prosthetic part 818 from the medical device. According toanother embodiment (not shown) the prosthetic part is held to themedical device solely using the elastic band 817, of course alsosupported by the remainder of the hip joint capsule and the affectedmuscles.

FIG. 30 shows the embodiment of the medical device according to FIG. 29,in a second state in which the elastic band 817 is stretched such thatthe prosthetic part 818 is released from the medical device. The elasticband 817 could be fixated to a fixation portion 814 of the prostheticcaput femur 812, and/or a fixating portion 815 of the medical deviceusing: at least one screw, at least one pin, formfitting, welding,adhesive, pin, wire, a ball mounted into a bowl, a male portion of onepart mounted into a female portion of the other part, a key introducedinto a lock being portions of said parts, band, or other mechanicalconnecting members. The failing of the rupture band 813 is preferablycaused by an abnormal movement of the hip joint, e.g. as the result ofthe patient falling. The elastic band 817 could comprise an elastic partor section, which could be the entire elastic band 818, made from anelastic material, such as an elastic polymer material such as: acopolymer material such as polystyrene, poly(ethylene-butylene) orpolystyrene. It is also conceivable that the material is a polyurethaneelastomeric material, polyamide elastomeric materials and polyesterelastomeric materials elastic copolymers of ethylene and at least onevinyl monomer such as, for example, vinyl acetates, unsaturatedaliphatic monocarboxylic acids, and esters of such monocarboxylic acids.The elastic band 813 could comprise a barrier coating, which cannot bepenetrated by body cells. Preferably, the bather coating comprises aParylene™ coating, or a biocompatible metal coating, such as gold,silver or titanium. According to other embodiments the elastic bandcomprises a spring type member, a combination of metal and plasticmaterials, a combination of metal and carbon based material or acombination of carbon and plastic based material.

FIG. 31 shows the hip joint in section in an embodiment where themedical device comprises a prosthetic part 819 adapted to be fixated tothe femoral bone 7. The prosthetic part comprises a prosthetic caputfemur which is adapted to comprise elastic elements 820 which act as areleasing member holding the prosthetic caput femur inside of themedical device fixated to the pelvic bone. The elastic elements 820 ofthe prosthetic caput femur, is preferably made of an elastic material,which for example could be an elastomeric polymer material or an elasticmetal material. It is conceivable that the elastic material comprises anouter layer in connection with the medical device which is adapted toresist the wear from the contact with the medical device. The elasticelement is adapted to compress when a pre-determined strain is placed onthe hip joint and thereby on the elastic elements 820. When the elasticelements 820 are compressed the prosthetic caput femur is released fromthe medical device.

FIG. 32 shows the medical device according to the embodiment shown inFIG. 31, in a second state, in which the elastic element 820 has beencompressed, following a pre-determined strain being placed on themedical device. The medical device is thereby placed in a second state,in which the prosthetic caput femur is released from the medical device,wherein it has been held.

FIG. 33 shows an embodiment of the medical device in which the elasticelements 820 are further assisted by a spring 821 in connection with twoelastic elements 820, the spring 821 is compressed alongside the elasticmembers 820, when a pre-determined strain is placed on the prostheticpart 819 comprising the prosthetic caput femur.

FIG. 34 shows the hip joint in section when a medical device for, in afirst state, holding the caput femur 5, or a prosthetic replacementtherefore, to the medical device, and in a second state releasing thecaput femur 5, or a prosthetic replacement therefore from the medicaldevice. The medical device is adapted to change from being in the firststate to being in the second state at a pre-determined strain affectingthe medical device by the connection with the pelvic bone 9 and thefemoral bone 7, which reduced the risk of the patient fracturing thefemoral bone 7 and/or the pelvic bone 9. The medical device comprisesmagnets 823 or magnetic material 823 placed in the medical device, andmagnets 822 or magnetic material 822 placed in the caput femur 5 or aprosthetic replacement therefore. According to one embodiment a magnet823 is placed in the medical device its south pole directed towards thecaput femur 5, or prosthetic replacement therefore, and a magnet 822placed in the caput femur 5, or prosthetic replacement therefore, havingits north pole directed towards the medical device. However only one ofthe sides needs to be magnetic whereas the other side merely needs tocomprise magnetic material. Any combination of north and south ends andmagnets/magnetic material is hence conceivable. The magnetic forcedescribed is adapted to hold the caput femur 5, or a prostheticreplacement therefore, in the medical device in normal use, enabling thehip joint to perform functional hip joint movements, and release thecaput femur 5, or a prosthetic replacement therefore, from the medicaldevice when a predetermined strain is exceeded.

FIG. 35 shows the medical device according to the embodiment of FIG. 30in the second state, in which the caput femur 5, or a prostheticreplacement therefore, is released from the medical device as a resultof a pre-determined level of strain being exceeded.

The medical device according to any of the embodiments could comprise atleast one material selected from a group consisting ofpolytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA) and fluorinatedethylene propylene (FEP). It is furthermore conceivable that thematerial comprises a metal alloy, such as cobalt-chromium-molybdenum ortitanium or stainless steel, or polyethylene, such as cross-linkedpolyethylene or gas sterilized polyethylene. The use of ceramic materialis also conceivable, in the contacting surfaces or the entire medicaldevice such as zirconium or zirconium dioxide ceramics or aluminaceramics. The part of the medical device in contact with human bone forfixation of the medical device to human bone could comprise a poorhousestructure which could be a porous micro or nano-structure adapted topromote the growth-in of human bone in the medical device for fixatingthe medical device. The porous structure could be achieved by applying ahydroxy-apatite (HA) coating, or a rough open-pored titanium coating,which could be produced by air plasma spraying, a combination comprisinga rough open-pored titanium coating and a HA top layer is alsoconceivable. The contacting parts could be made of a self lubricatedmaterial such as a waxy polymer, such as PTFE, PFA, FEP, PE and UHMWPE,or a powder metallurgy material which could be infused with a lubricant,which preferably is a biocompatible lubricant such as a Hyaluronic acidderivate. It is also conceivable that the material of contacting partsor surfaces of the medical device herein is adapted to be constantly orintermittently lubricated. According to some embodiments the parts orportions of the medical device could comprise a combination of metalmaterials and/or carbon fibers and/or boron, a combination of metal andplastic materials, a combination of metal and carbon based material, acombination of carbon and plastic based material, a combination offlexible and stiff materials, a combination of elastic and less elasticmaterials, Corian or acrylic polymers.

Please note that any embodiment or part of embodiment as well as anymethod or part of method could be combined in any way. All examplesherein should be seen as part of the general description and thereforepossible to combine in any way in general terms.

1. A medical device for implantation in a hip joint of a patient,wherein said medical device is adapted to be fixated to the pelvic boneof the patient, and wherein said medical device comprises an inner andan outer surface, wherein a contacting portion, of said inner surface isspherical and adapted to face the center of the hip joint when saidmedical device is implanted, and wherein said medical device is adaptedto receive a caput femur or a prosthetic replacement therefor having aspherical portion, wherein said medical device comprises at least oneextending portion, extending said contacting portion of said innersurface such that said at least one extending portion clasps saidspherical portion of said caput femur, or a prosthetic replacementtherefor, such that said spherical portion is restrained in said medicaldevice.
 2. The medical device according to claim 1, wherein said medicaldevice is adapted to receive a caput femur or a prosthetic replacementtherefor having a collum femur or prosthetic collum femur fixated tosaid spherical portion of said caput femur or prosthetic replacementtherefor, wherein: a) said inner surface comprises an equator line,being the largest circular circumference of said inner contactingsurface, being a surface adapted to be in contact with said caput femur,or prosthetic replacement therefor, and b) said at least one extendingportion passes beyond said equator line, such that the end portion ofsaid contacting portion of said inner surface forms a circular extensionline having a smaller circumference than said equator line, and c) saidat least one extending portion circumferentially extends discontinuouslyalong said equator line, such that a portion of said collum femur orprosthetic replacement therefor can be placed between said extensionline and said equator line.
 3. A medical device for implantation in ahip joint, wherein said medical device is adapted to receive a caputfemur or a prosthetic replacement therefor having a collum femur orprosthetic collum femur fixated to said spherical portion of said caputfemur or prosthetic replacement therefor, wherein: d) an inner surfacecomprises an equator line, being the largest circular circumference ofsaid inner surface, e) at least one extending portion passes beyond saidequator line, such that the end portion of said contacting portion ofsaid inner surface forms a parallel circular extension line having asmaller circumference than said equator line, and f) said at least oneextending portion circumferentially extends discontinuously along saidequator line, such that a portion of said collum femur or prostheticreplacement therefor can be placed between said extension line and saidequator line.
 4. The medical device according to claim 2, wherein saidextension line is placed distal to the equator line, when the medicaldevice is implanted.
 5. The medical device according to claim 1, whereinsaid at least one extending portion extends circumferentially along saidequator line, dorsal to the right-left axis of pelvis.
 6. The medicaldevice according to claim 1, wherein said at least one extending portionextends circumferentially along said equator line, dorsal to the coronalpelvis plane PXY and proximal to the horizontal pelvis PXZ plane.
 7. Themedical device according to claim 1, wherein said at least one extendingportion extends circumferentially along said equator line, dorsal to thecoronal pelvis plane PXY and distal to the horizontal pelvis PXZ plane.8. The medical device according to claim 1, wherein one extendingportion extends circumferentially along said equator line dorsal to thecoronal pelvis plane PXY and proximal to the horizontal pelvis PXZplane, and one extending portion extends dorsal to the coronal pelvisplane PXY and distal to the horizontal pelvis PXZ plane.
 9. The medicaldevice according to claim 2, wherein said at least one extending portionextends circumferentially along said equator line, in the proximalquadrant of the equator line.
 10. The medical device according to claim2, wherein said at least one extending portion extends circumferentiallyalong said equator line, in the distal quadrant of the equator line. 11.The medical device according to claim 2, wherein two extending portionsextends circumferentially along said equator line, in the distal andproximal quadrant thereof.
 12. The medical device according to claim 2,wherein said at least one extending portion extends circumferentiallyalong said equator line, in the proximal and dorsal quadrant thereof.13. The medical device according to claim 2, wherein said at least oneextending portion extends circumferentially along said equator line, inthe distal and dorsal quadrant thereof.
 14. The medical device accordingto claim 2, wherein at least one extending portion extendscircumferentially along said equator line, in the distal, dorsal andproximal quadrant thereof.
 15. The medical device according to claim 2,wherein at least a first portion of said medical device is an extendingportion, extending beyond said circular equator line, and at least asecond portion is a portion not extending beyond said circular equatorline, wherein said second portion circumferentially extends along atleast ¼ of said circular equator line.
 16. The medical device accordingto claim 2, wherein at least a first portion of said medical device isan extending portion, extending beyond said circular equator line, andat least a second portion is a portion not extending beyond saidcircular equator line, wherein said second portion circumferentiallyextends along at least ⅓ of said circular equator line.
 17. The medicaldevice according to claim 2, wherein at least a first portion of saidmedical device is an extending portion, extending beyond said circularequator line, and at least a second portion is a portion not extendingbeyond said circular equator line, wherein said second portioncircumferentially extends along at least ½ of said circular equatorline.
 18. The medical device according to claim 2, wherein at least afirst portion of said medical device is an extending portion, extendingbeyond said circular equator line, and at least a second portion is aportion not extending beyond said circular equator line, wherein saidfirst portion circumferentially extends along at least ¼ of saidcircular equator line.
 19. The medical device according to claim 2,wherein at least a first portion of said medical device is an extendingportion, extending beyond said circular equator line, and at least asecond portion is a portion not extending beyond said circular equatorline, wherein said first portion circumferentially extends along atleast ⅓ of said circular equator line.
 20. The medical device accordingto claim 2, wherein at least a first portion of said medical device isan extending portion, extending beyond said circular equator line, andat least a second portion is a portion not extending beyond saidcircular equator line, wherein said first portion circumferentiallyextends along at least ½ of said circular equator line. 21.-47.(canceled)